Treatment of schizophrenia and psychosis

ABSTRACT

The compound 5-(2-ethyl-2H-tetrazol-5-yl)-1,2,3,6-tetrahydro-1-methylpyridine has shown effects on models of psychosis, schizophrenia and schizophreniform diseases and is useful for the manufacture of a pharmaceutical preparation for the treatment of such diseases.

This is a 371 of PCT/DK98/00220 filed May 28, 1998.

FIELD OF INVENTION

The present invention relates to the use of 5-(2-ethyl-2H-tetrazol-5-yl)-1,2,3,6-tetrahydro-1-methylpyridine for the treatment of psychosis.

BACKGROUND OF THE INVENTION

EP-A1 0 296 721 disclosed a class of piperidine or 1,2,3,6-terahydropyridine compounds substituted in the 5-position with a five-membered heterocyclic group, including a subclass of optionally substituted 5-tetrazolyl-1,2,3,6-tetrahydro-pyridine compounds. The compounds were disclosed to have high affinity to central cholinergic receptors, in particular high affinity for central muscarinic M₁ receptors, thus being useful in the treatment of Alzheimer's disease, senile dementia, and impaired learning and memory functions.

The structure-activity relationship of this subclass was described by Moltzen et al., J. Med. Chem. 1994, 37, 4085-4099. One of the compounds, i.e. 5-(2-ethyl-2H-tetrazol-5-yl)-1,2,3,6-tetrahydro-1-methylpyridine has been reported to be selective for muscarinic receptors with a several fold higher affinity for M₁ than for M₂ and M₃ receptors (Subtypes of Muscarinic Receptors, The Sixth International Symposium, Nov. 9-12, 1994, Fort Lauderdale). Functionally, it has been described to behave as a partial agonist at M₁ receptors and an antagonist at M₂ and M₃ receptors. Furthermore, the only prominent in vivo effect reported was effect on spatial memory acquisition in young and aged rats, respectively. Recently, the compound was disclosed to show relieving effects after traumatic brain injury, WO 97/17074.

A class of compounds previously reported to show muscarinic effects were described to be useful in the treatment of schizophrenia, cf. WO 9505174 A1 and WO 95/05379.

It has now, surprisingly, been found that the compound 5-(2-ethyl-2H-tetrazol-5-yl)1,2,3,6-tetrahydro-1-methylpyridine shows beneficial effects in the treatment of psychosis, schizophrenia, and schizophreniform diseases.

SUMMARY OF THE INVENTION

Accordingly, the present invention relates to the use of 5-(2-ethyl-2H-tetrazol-5-yl)-1,2,3,6-tetrahydro-1-methylpyridine or an acid addition salt thereof

for the manufacture of a pharmaceutical preparation for the treatment of psychosis, schizophrenia, and schizophreniform diseases.

The term psychosis is in this specification meant to include all forms of psychoses, such as organic psychoses, drug induced psychoses, Alzheimer related psychoses, and psychosis or related conditions associated with other mental disorders, such as paranoid personality disorder, etc.

The terms schizophrenia and schizophreniform diseases include all types of such disorders, e.g. catatonic, disorganised, paranoid, undifferential and residual schizophrenia, and all conditions associated with such diseases, including positive and negative symptoms thereof.

The pharmaceutically acceptable acid addition salts of the compounds used in the invention are salts formed with non-toxic organic or inorganic acids. Exemplary of such organic salts are those with maleic, fumaric, benzoic, ascorbic, pamoic, succinic, oxalic, bis-methylenesalicylic, methanesulfonic, ethanedisulfonic, acetic, propionic, tartaric, salicylic, citric, gluconic, lactic, malic, mandelic, cinnamic, citraconic, aspartic, stearic, palmitic, itaconic, glycolic, p-amino-benzoic, glutamic, benzene sulfonic, and theophylline acetic acids, as well as the 8-halotheophyllines, for example 8-bromo-theophylline. Exemplary of such inorganic salts are those with hydrochloric, hydrobromic, sulfuric, sulfamic, phosphoric, and nitric acids.

The compound used according to the invention has now been found to be useful in the treatment of psychosis, schizophrenia, and schizophreniform diseases. So, it inhibits the effects of phencyclidine (PCP) on social interaction and PCP-induced stereotyped behaviour in rats. The effects of PCP on social interaction and other behavioural features and an animal model based thereon has been described by F. Sams-Dodd in Behavioural Pharmacology, 1996, 7, 3-23. The study of F. Sams-Dodd suggests that PCP-induced stereotyped behaviour and social isolation, respectively, in rats correspond to positive and negative symptoms of schizophrenia, and that PCP-treated rats respond to drug treatment in a manner that correlates well with findings in schizophrenic patients. Thus this model may determine effects of drugs on positive and negative symptoms of schizophrenia, onset of action, and side effect profile.

In another aspect, the present invention provides a method for treatment of psychosis, schizophrenia, and schizophreniform diseases in humans, comprising the step of administering a therapeutically effective amount of 5-(2-ethyl-2H-tetrazol-5-yl)-1,2,3,6-tetrahydro-1-methylpyridine or an acid addition salt thereof to a patient in need thereof.

The compound used according to the invention and the pharmaceutically acceptable acid addition salts thereof may be administered in any suitable way, e.g. orally or parenterally, and the compounds may be presented in any suitable form for such administration, e.g. in the form of tablets, capsules, powders, syrups, or solutions or dispersions for injection.

An effective daily dose of the compound according to the invention or a pharmaceutically acceptable salt thereof is from 10 μg/kg to 10 mg/kg body weight, preferably 25 mg/day/kg body weight to 1.0 mg/day/kg body weight. Accordingly, a suitable daily dose is 500 μg to 600 mg/day, preferably 1.0 mg to 100 mg.

The compound used according to the invention may be obtained as described in EP-A1 0 296 721 and the acid addition salts thereof are easily prepared by methods well known in the art.

Pharmacology

The compound used according to the invention was tested by the method described by F. Sams-Dodd, 1996, supra:

Phencyclidine-induced stereotyped behaviour and social isolation in rats. Young male Witar rats (Charles River, Germany) weighing 320-420 g were used. The rats were kept in a reversed light cycle (light 18.00 h-06.00 h). Further details regarding the design of the model appears from F. Sams-Dodd, 1996, supra: and F. Sams-Dodd, J. Neurosci. Methods. 59, 1995, 157-168.

The test was performed in an open arena (L, W, H: 150×100×40 cm) with bottom and sides covered with a black non-reflecting material. The behaviour of the rats were recorded by a video camera.

The rats were placed in the experimental room one day before testing. During the test period the rats received daily injections s.c. with test compound and PCP (7.1 μmol/kg) for three days. 30 mins after the last injection and in the period from 08.00 h to 14.00 h the rats were subjected to the test. Two rats, one white and one coloured black, having received identical treatment and being unfamiliar to each other, were placed in the unfamiliar test arena. The rats were videofilmed for 10 mins and returned to their cages. Rats receiving test compound and vehicle were used as control groups.

The social interaction between the rats were analysed as described in the above references. The following parameters were determined:

Travelled Distance: Total travelled distance during the observation period. This is a measure of locomotor activity.

Percent time in central zone: The arena was divided in a central and a peripheral zone that covered 33% and 66% of the arena, respectively.

Social Interaction: Duration of social behaviour between the rats during the observation period measured as the number of observations in which the centres of gravity of the rats were closer than 20 cm apart. This number was divided by the sampling rate to express the parameter in seconds.

Active social interaction: Duration of social behaviour while the rat was actively moving around.

Passive social interaction: Duration of social behaviour while the rat was inactive.

Stereotyped behaviour and ataxia were rated off-line by trained observers. Each videorecording was viewed for 60 s halfway through the 10 min. observation period, and each rat was scored after the scales of Castellani and Adams Eur. J. Pharmacol., 73, 1981, 143-154, as described in F. Sams-Dodd, 1996, supra.

Results

The compound of the invention was found to improve active social interaction in PCP-treated rats in doses of 5 μmol/kg or larger. Furthermore, it inhibits PCP-induced stereotyped behaviour in rats.

FORMULATION EXAMPLES

The pharmaceutical formulations of the invention may be prepared by conventional methods in the art.

For example: Tablets may be prepared by mixing the active ingredient with ordinary adjuvants and/or diluents and subsequently compressing the mixture in a conventional tabletting machine. Examples of adjuvants or diluents comprise: corn starch, lactose, talcum, magnesium stearate, gelatine, lactose, gums, and the like. Any other adjuvant or additive colourings, aroma, preservatives etc. may be used provided that they are compatible with the active ingredients. Solutions for injections may be prepared by solving the active ingredient and possible additives in a part of the vehicle, preferably sterile water, adjusting the solution to the desired volume, sterilization of the solution, and filling in suitable ampules or vials. Any suitable additive conventionally used in the art may be added, such as tonicity agents, preservatives, antioxidants, etc.

Typical examples of recipes for the formulations of the invention are as follows (amounts of active ingredient calculated as the free base):

1) Tablets: Comp. of invention 20 mg Lactose 60 mg Maize starch 30 mg Hydroxypropylcellulose 2.4 mg Microcrystalline cellulose 19.2 mg Croscarmellose Sodium Type A 2.4 mg Magnesium stearate 0.84 mg 2) Tablets: Comp. of invention 10 mg Lactose 46.9 mg Maize starch 23.5 mg Povidone 1.8 mg Microcrystalline cellulose 14.4 mg Croscarmellose Sodium Type A 1.8 mg Magnesium stearate 0.63 mg 3) Syrup: Comp. of invention 5.0 mg Sorbitol 500 mg Hydroxypropylcellulose 15 mg Glycerol 50 mg Methyl-paraben 1 mg Propyl-paraben 0.1 mg Ethanol 0.005 ml Flavour 0.05 mg Saccharin sodium 0.5 mg Water ad 1 ml 4) Solution: Comp. of invention 1.0 mg Sorbitol 5.1 mg Acetic acid 0.08 mg Water for injection ad 1 ml 

What is claimed is:
 1. A method of treating psychosis, schizophrenia and schizophreniform diseases, comprising administering a therapeutically effective amount of 5-(2-ethyl-2H-tetrazol-5-yl)- 1,2,3,6-tetrahydro-1-methylpyridine (Formula (I))

or a pharmaceutically acceptable acid addition salt thereof, to a person in need of said treatment.
 2. The method of claim 1, wherein 5-(2-ethyl-2H-tetrazol-5-yl)-1,2,3,6-tetrahydro-1-methylpyridine or a pharmaceutically acceptable acid addition salt thereof is in unit dosage form.
 3. The method of claim 2, wherein 5-(2-ethyl-2H-tetrazol-5-yl)-1,2,3,6-tetrahydro-1-methylpyridine or a pharmaceutically acceptable acid addition salt thereof is present in an amount of 500 μg to 600 mg per day.
 4. The method of claim 2, wherein 5-(2-ethyl-2H-tetrazol-5-yl)-1,2,3,6-tetrahydro-1-methylpyridine or a pharmaceutically acceptable acid addition salt thereof is present in an amount of 1.0 mg to 100 mg per day.
 5. The method of claim 1, for treating positive and negative symptoms of schizophrenia.
 6. The method of claim 5, for treating positive symptoms of schizophrenia. 